Three digit numbers with repeated digits

Total 3-digit numbers from 100 to 999 = $999 - 100 + 1 = 900$.

Number of 3-digit integers with ALL digits distinct:

• First digit (hundreds): 9 choices ($1-9$)
• Second digit (tens): 9 choices ($0-9$ excluding hundreds digit)
• Third digit (units): 8 choices ($0-9$ excluding first two digits) Total distinct digit numbers = $9 \times 9 \times 8 = 648$.

Numbers with at least one digit repeated = $900 - 648 = 252$.